Noble metal thermocouples, such as Type-R (Pt-13% Rh vs. Pt) and Type-S (Pt-10% Rh vs. Pt) thermocouples, among others, may be used for measuring hot gas temperatures in excess of 1300° C. For turbine applications, thermocouple probes typically are on the order of 10 cm–30 cm in length. Noble metal extension wires, thermoelectrically matched or compensating type to the thermoelements of such a thermocouple, may be used to bridge a distance between a distal end of the thermocouple and electrical circuitry configured to receive and process its output. The circuit extension may also include terminal connections to facilitate probe installation and maintenance.
Under certain conditions, it may become necessary to have very long extension wires. This may happen, for example, where the geometry and physical constraints of the object producing the hot gases to be measured, and the location within the object where these hot gases are accessible, are such that the electrical circuitry cannot be placed nearby. For noble metal thermocouples, the extension wires and terminal components may not be commercially available or cost prohibitive for the required length.